The polymerization of 1,3-dienes to rubbery polymers, such as polybutadiene, using a butyl lithium catalyst in a hydrocarbon diluent normally yields a polymer containing 90% 1,4-microstructure and 10% 1,2-microstructure. Diene polymers and copolymers having increased 1,2-microstructure content have become of interest for use in applications such as for tire rubbers, molded rubber goods, molding compounds, surface coatings and the like.
It has now been discovered that increased percentages of 1,2-microstructure can be obtained by carrying out the polymerization in the presence of a modifier compound of a linear or cyclic oligomeric oxolanyl alkane.